High magnetoresistance spin valve sensor with self-pinned antiparallel (AP) pinned layer structure

ABSTRACT

A spin valve sensor includes a spacer layer which is located between a free layer and an antiparallel (AP) pinned layer structure wherein the AP pinned layer structure includes an antiparallel coupling layer which is located between and interfaces first and second AP pinned layers with the second AP pinned layer interfacing the spacer layer. Each of the first and second AP pinned layers is composed of cobalt iron (CoFe) wherein the iron (Fe) content in the cobalt iron (CoFe) of one of the first and second AP pinned layers is greater than the iron (Fe) content in the cobalt iron (CoFe) in the other one of the first and second AP pinned layers.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a high magnetoresistance spinvalve sensor with a self-pinned AP pinned layer structure and, moreparticularly, to an AP pinned layer structure wherein AP pinned layersemploy different materials for optimizing a magnetoresistive coefficientdr/R and for self-pinning one another.

[0003] 2. Description of the Related Art

[0004] The heart of a computer is a magnetic disk drive which includes arotating magnetic disk, a slider that has write and read heads, asuspension arm above the rotating disk and an actuator arm. Thesuspension arm biases the slider into contact with the surface of thedisk when the disk is not rotating but, when the disk rotates, air isswirled by the rotating disk adjacent an air bearing surface (ABS) ofthe slider causing the slider to ride on an air bearing a slightdistance from the surface of the rotating disk. When the slider rides onthe air bearing the actuator arm swings the suspension arm to place thewrite and read heads over selected circular tracks on the rotating diskwhere field signals are written and read by the write and read heads.The write and read heads are connected to processing circuitry thatoperates according to a computer program to implement the writing andreading functions.

[0005] An exemplary high performance read head employs a spin valvesensor for sensing the magnetic field signals from the rotating magneticdisk. The sensor includes a nonmagnetic electrically conductive firstspacer layer sandwiched between a ferromagnetic pinned layer structureand a ferromagnetic free layer structure. An antiferromagnetic pinninglayer typically interfaces the pinned layer structure for pinning amagnetic moment of the pinned layer structure 90° to the air bearingsurface (ABS) wherein the ABS is an exposed surface of the sensor thatfaces the magnetic disk. First and second leads are connected to thespin valve sensor for conducting a sense current therethrough. Amagnetic moment of the free layer structure is free to rotate upwardlyand downwardly with respect to the ABS from a quiescent or bias pointposition in response to positive and negative magnetic field signalsfrom the rotating magnetic disk. The quiescent position, which ispreferably parallel to the ABS, is the position of the magnetic momentof the free layer structure with the sense current conducted through thesensor in the absence of field signals.

[0006] The thickness of the spacer layer is chosen so that shunting ofthe sense current and a magnetic coupling between the free and pinnedlayer structures are minimized. This thickness is typically less thanthe mean free path of electrons conducted through the sensor. With thisarrangement, a portion of the conduction electrons are scattered at theinterfaces of the spacer layer with the pinned and free layerstructures. When the magnetic moments of the pinned and free layerstructures are parallel with respect to one another scattering isminimal and when their magnetic moments are antiparallel scattering ismaximized. Changes in scattering changes the resistance of the spinvalve sensor as a function of cos θ, where θ is the angle between themagnetic moments of the pinned and free layer structures. Thesensitivity of the sensor is quantified as magnetoresistive coefficientdr/R where dr is the change in the resistance of the sensor as themagnetic moment of the free layer structure rotates from a positionparallel with respect to the magnetic moment of the pinned layerstructure to an antiparallel position with respect thereto and R is theresistance of the sensor when the magnetic moments are parallel.

[0007] In addition to the spin valve sensor the read head includesnonconductive nonmagnetic first and second read gap layers andferromagnetic first and second shield layers. The spin valve sensor islocated between the first and second read gap layers and the first andsecond read gap layers are located between the first and second shieldlayers. In the construction of the read head the first shield layer isformed first followed by formation of the first read gap layer, the spinvalve sensor, the second read gap layer and the second shield layer.Spin valve sensors are classified as a top spin valve sensor or a bottomspin valve sensor depending upon whether the pinning layer is locatednear the bottom of the sensor close to the first read gap layer or nearthe top of the sensor close to the second read gap layer. Spin valvesensors are further classified as simple pinned or antiparallel (AP)pinned depending upon whether the pinned layer structure is one or moreferromagnetic layers with a unidirectional magnetic moment or a pair offerromagnetic AP layers that are separated by a coupling layer withmagnetic moments of the ferromagnetic AP layers being antiparallel toone another. Spin valve sensors are still further classified as singleor dual wherein a single spin valve sensor employs only one pinned layersructure and a dual spin valve sensor employs two pinned layerstructures with the free layer structure located therebetween.

[0008] As stated hereinabove, a magnetic moment of the aforementionedpinned layer structure is pinned 90° to the ABS by the aforementionedantiferromagnetic (AFM) pinning layer. After deposition of the sensor,the sensor is subjected to a temperature at or near a blockingtemperature of the material of the pinning layer in the presence of afield which is oriented perpendicular to the ABS for the purpose ofresetting the orientation of the magnetic spins of the pinning layer.The elevated temperature frees the magnetic spins of the pinning layerso that they align perpendicular to the ABS. This also aligns themagnetic moment of the pinned layer structure perpendicular to the ABS.When the read head is cooled to ambient temperature the magnetic spinsof the pinning layer are fixed in the direction perpendicular to the ABSwhich pins the magnetic moment of the pinned layer structureperpendicular to the ABS. After resetting the pinning layer it isimportant that subsequent elevated temperatures and extraneous magneticfields do not disturb the setting of the pinning layer. It is alsodesirable that the pinning layer be as thin as possible since it islocated within the track width of the sensor and its thickness adds toan overall gap length between the first and second shield layers. Itshould be understood that the thinner the gap length the higher thelinear read bit density of the read head. This means that more bits canbe read per inch along the track of a rotating magnetic disk whichenables an increase in the storage capacity of the magnetic disk drive.

[0009] A scheme for minimizing the aforementioned gap between the firstand second shield layers is to provide a self-pinned AP pinned layerstructure. The self-pinned AP pinned layer structure eliminates the needfor the aforementioned pinning layer which permits the read gap to bereduced by 150 Å when the pinning layer is platinum manganese (PtMn). Inthe self-pinned AP pinned layer structure each AP pinned layer has anintrinsic uniaxial anisotropy field and a magnetostriction uniaxialanisotropy field. The intrinisic uniaxial anisotropy field is due to theintrinsic magnetization of the layer and the magnetostriction uniaxialanisotropy field is a product of the magnetostriction of the layer andstress within the layer. A positive magnetostriction of the layer andcompressive stress therein to the ABS results in a magnetostrictionuniaxial anisotropy field that can support an intrinsic uniaxialanisotropy field. The orientations of the magnetic moments of the APpinned layers are set by an external field. This is accomplished withoutthe aforementioned elevated temperature which is required to free themagnetic spins of the pinning layer.

[0010] If the self-pinning of the AP pinned layer structure is notsufficient, unwanted extraneous fields can disturb the orientations ofthe magnetic moments of the AP pinned layers or, in a worst situation,could reverse their directions. Accordingly, there is a strong-felt needto maximize the uniaxial magnetostriction anisotropy field whilemaintaining a high magnetoresistive coefficient dr/R of the spin valvesensor.

SUMMARY OF THE INVENTION

[0011] The present invention employs cobalt iron (CoFe) for each of thefirst and second AP pinned layers in a self-pinned AP pinned layerstructure, however, the iron (Fe) content in the cobalt iron (CoFe) inthe first and second AP pinned layers is different for improving themagnetostriction uniaxial anisotropy field while maintaining a highmagnetoresistive coefficient dr/R. In a broad aspect of the inventionthe iron content in the cobalt iron (CoFe) of one of the first andsecond AP pinned layers is greater than the iron content in the cobaltiron (CoFe) in the other of the first and second AP pinned layers. Inone embodiment of the invention the iron content in the cobalt iron(CoFe) in the first AP pinned layer, which does not interface the spacerlayer, is greater than the iron content in the cobalt iron (CoFe) in thesecond AP pinned layer which interfaces the spacer layer. One of ourexperiments shows that when the content of the first AP pinned layercomprises Co₆₀Fe₄₀ and the content of the second AP pinned layercomprises Co₉₀Fe₁₀ the magnetostriction uniaxial anisotropy field issignificantly improved while maintaining a high magnetoresistivecoefficient dr/R.

[0012] In another embodiment of the invention the iron content in thecobalt iron (CoFe) in the second AP pinned layer is greater than theiron content in the cobalt iron (CoFe) in the first AP pinned layer. Instill another one of our experiments the second AP pinned layer includeda second film which is located between first and third films wherein theiron content in the cobalt iron (CoFe) in the second film was greaterthan the iron content in the cobalt iron (CoFe) in each of the first andthird films. In this experiment the content of the second film comprisedCo₆₀Fe₄₀ and the content of each of the first and third films comprisedCo₉₀Fe₁₀. From these experiments a still further embodiment is derivedwherein the first AP pinned layer comprises Co₆₀Fe₄₀ and the second APpinned layer comprises the aforementioned first, second and third films.

[0013] An object of the present invention is to provide a spin valvesensor with a self-pinned AP pinned layer structure wherein theself-pinning and amplitude output are improved while maintaining a highmagnetoresistive coefficient dr/R.

[0014] Another object is to provide a method of making theaforementioned spin valve sensor.

[0015] Other objects and attendant advantages of the invention will beappreciated upon reading the following description taken together withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a plan view of an exemplary magnetic disk drive;

[0017]FIG. 2 is an end view of a slider with a magnetic head of the diskdrive as seen in plane 2-2 of FIG. 1;

[0018]FIG. 3 is an elevation view of the magnetic disk drive whereinmultiple disks and magnetic heads are employed;

[0019]FIG. 4 is an isometric illustration of an exemplary suspensionsystem for supporting the slider and magnetic head;

[0020]FIG. 5 is an ABS view of the magnetic head taken along plane 5-5of FIG. 2;

[0021]FIG. 6 is a partial view of the slider and a merged magnetic headas seen in plane 6-6 of FIG. 2;

[0022]FIG. 7 is a partial ABS view of the slider taken along plane 7-7of FIG. 6 to show the read and write elements of the merged magnetichead;

[0023]FIG. 8 is a view taken along plane 8-8 of FIG. 6 with all materialabove the coil layer and leads removed;

[0024]FIG. 9 is an enlarged isometric ABS illustration of the read headwith a prior art spin valve sensor;

[0025]FIG. 10 is an ABS view of a prior art spin valve sensor whichemploys a pinning layer for pinning magnetic moments of an AP pinnedlayer structure;

[0026]FIG. 11 is an ABS view of a first embodiment of the present spinvalve sensor;

[0027]FIG. 12 is an ABS view of a second embodiment of the present spinvalve sensor;

[0028]FIG. 13 is an ABS view of a spin valve sensor tested by us;

[0029]FIG. 14 is an ABS view of a third embodiment of the present spinvalve sensor; and

[0030]FIG. 15 is an ABS view of a fourth embodiment of the present spinvalve sensor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Magnetic Disk Drive

[0032] Referring now to the drawings wherein like reference numeralsdesignate like or similar parts throughout the several views, FIGS. 1-3illustrate a magnetic disk drive 30. The drive 30 includes a spindle 32that supports and rotates a magnetic disk 34. The spindle 32 is rotatedby a spindle motor 36 that is controlled by a motor controller 38. Aslider 42 has a combined read and write magnetic head 40 and issupported by a suspension 44 and actuator arm 46 that is rotatablypositioned by an actuator 47. A plurality of disks, sliders andsuspensions may be employed in a large capacity direct access storagedevice (DASD) as shown in FIG. 3. The suspension 44 and actuator arm 46are moved by the actuator 47 to position the slider 42 so that themagnetic head 40 is in a transducing relationship with a surface of themagnetic disk 34. When the disk 34 is rotated by the spindle motor 36the slider is supported on a thin (typically, 0.01 μm) cushion of air(air bearing) between the surface of the disk 34 and the air bearingsurface (ABS) 48. The magnetic head 40 may then be employed for writinginformation to multiple circular tracks on the surface of the disk 34,as well as for reading information therefrom. Processing circuitry 50exchanges signals, representing such information, with the head 40,provides spindle motor drive signals for rotating the magnetic disk 34,and provides control signals to the actuator for moving the slider tovarious tracks. In FIG. 4 the slider 42 is shown mounted to a suspension44. The components described hereinabove may be mounted on a frame 54 ofa housing 55, as shown in FIG. 3.

[0033]FIG. 5 is an ABS view of the slider 42 and the magnetic head 40.The slider has a center rail 56 that supports the magnetic head 40, andside rails 58 and 60. The rails 56, 58 and 60 extend from a cross rail62. With respect to rotation of the magnetic disk 34, the cross rail 62is at a leading edge 64 of the slider and the magnetic head 40 is at atrailing edge 66 of the slider.

[0034]FIG. 6 is a side cross-sectional elevation view of a mergedmagnetic head 40, which includes a write head portion 70 and a read headportion 72, the read head portion employing a spin valve sensor 74 ofthe present invention. FIG. 7 is an ABS view of FIG. 6. The spin valvesensor 74 is sandwiched between nonmagnetic electrically insulativefirst and second read gap layers 76 and 78, and the read gap layers aresandwiched between ferromagnetic first and second shield layers 80 and82. In response to external magnetic fields, the resistance of the spinvalve sensor 74 changes. A sense current Is conducted through the sensorcauses these resistance changes to be manifested as potential changes.These potential changes are then processed as readback signals by theprocessing circuitry 50 shown in FIG. 3.

[0035] The write head portion 70 of the magnetic head 40 includes a coillayer 84 which is sandwiched between first and second insulation layers86 and 88. A third insulation layer 90 may be employed for planarizingthe head to eliminate ripples in the second insulation layer caused bythe coil layer 84. The first, second and third insulation layers arereferred to in the art as an “insulation stack”. The coil layer 84 andthe first, second and third insulation layers 86, 88 and 90 aresandwiched between first and second pole piece layers 92 and 94. Thefirst and second pole piece layers 92 and 94 are magnetically coupled ata back gap 96 and have first and second pole tips 98 and 100 which areseparated by a write gap layer 102 at the ABS. Since the second shieldlayer 82 and the first pole piece layer 92 are a common layer this headis known as a merged head. In a piggyback head (not shown) the layers 82and 92 are separate layers and are separated by an insulation layer. Asshown in FIGS. 2 and 4, first and second solder connections 104 and 106connect leads from the spin valve sensor 74 to leads 112 and 114 on thesuspension 44, and third and fourth solder connections 116 and 118connect leads 120 and 122 from the coil 84 (see FIG. 8) to leads 124 and126 on the suspension.

[0036]FIG. 9 is an isometric ABS illustration of the read head 40 shownin FIG. 7. The read head 40 includes the spin valve sensor 74. First andsecond hard bias and lead layers 134 and 136 are connected to first andsecond side edges 138 and 139 of the spin valve sensor. This connectionis known in the art as a contiguous junction and is fully described incommonly assigned U. S. Pat. No. 5,018,037. The first hard bias and leadlayers 134 include a first hard bias layer 140 and a first lead layer142 and the second hard bias and lead layers 136 include a second hardbias layer 144 and a second lead layer 146. The hard bias layers 140 and144 cause magnetic fields to extend longitudinally through the spinvalve sensor 74 for stabilizing the magnetic domains therein. The spinvalve sensor 74 and the first and second hard bias and lead layers 134and 136 are located between the nonmagnetic electrically insulativefirst and second read gap layers 76 and 78 and the first and second readgap layers 76 and 78 are, in turn, located between the ferromagneticfirst and second shield layers 80 and 82.

EXAMPLES

[0037] Examples 1-5 were tested at the coupon level and Examples 1 and 2were further tested at the row level. At the coupon level a singlesensor is fabricated on a glass substrate and is not lapped to the ABS.Since lapping causes the aforementioned ABS compressive stress the ABScompressive stress due to lapping is not present at the coupon level.The row level is a row of read heads including their read sensors and istaken from a slider substrate where rows and columns of such read headshave been fabricated. After dicing the row of read heads from the slidersubstrate, the row is lapped to the ABS which causes the aforementionedcompressive stress.

[0038] At the coupon level the magnetoresistive coefficient dr/R, theintrinsic uniaxial anisotropy field H_(Ki), the magnetostriction λ (AP)of the AP pinned layers, the magnetostriction uniaxial anisotropy fieldH_(Kλ), the resistance of the sensor R_(S) and the magnetostriction ofthe free layer λ (FL) were determined and/or calculated. At the rowlevel Examples 1 and 2 were tested for amplitude output.

Example 1

[0039] A prior art spin valve sensor 200, as shown in FIG. 10, was builtand tested. The spin valve sensor includes a spacer layer (S) 202 whichis located between an AP pinned layer structure 204 and a free layerstructure 206. An antiferromagnetic (AFM) pinning layer 208 interfacesthe AP pinned layer structure 204 and pins magnetic moments therein,which will be described in more detail hereinafter. A seed layerstructure 210, which includes first, second and third seed layers (SL1),(SL2) and (SL3) 212, 214 and 216, interfaces the pinning layer 208 andis composed of materials which promote a desirable texture of the layersdeposited thereon. The free layer structure 206 includes first andsecond free layers (FL1) and (FL2) 218 and 220. It has been found thatwhen the first free layer 218 is composed of cobalt iron (CoFe) thatthere is an improvement in the magnetoresistive coefficient dr/R of thespin valve sensor. A cap layer structure 222 is provided on top of thefree layer structure 206 for protecting it from subsequent processingsteps. The cap layer structure may include first and second cap layers(CAP1) and (CAP2) 224 and 226. Again, when the first cap layer 224 iscomposed of copper (Cu) it has been found that there is an increase inmagnetoresistive coefficient dr/R.

[0040] The AP pinned layer structure 204 includes an antiparallelcoupling layer (APC) 230 which is located between first and second APpinned layers (AP1) and (AP2) 232 and 234. The pinning layer 208interfaces the first AP pinned layer 232 and pins a magnetic moment 236of the first AP pinned layer perpendicular to the ABS in a direction outof the sensor or into the sensor, as shown in FIG. 10. By a strongantiparallel coupling between the first and second AP pinned layers 232and 234 the magnetic moment 238 of the second AP pinned layer 234 isantiparallel to the magnetic moment 236. The free layer structure 206has a magnetic moment 240 which is parallel to the ABS in a directionfrom right to left or from left to right, as shown in FIG. 10. A sensecurrent I_(S) is conducted through the sensor parallel to the majorplanes of the thin film layers in a direction from right to left or fromleft to right, as shown in FIG. 10. When a field signal from therotating magnetic disk 34 in FIG. 1 rotates the magnetic moment 240 ofthe free layer structure into the sensor the magnetic moments 240 and238 become more antiparallel which increases the resistance of the spinvalve sensor to the sense current I_(S) and when a field signal from therotating magnetic disk rotates the magnetic moment 240 out of the sensorthe magnetic moments 240 and 238 become more parallel which reduces theresistance of the spin valve sensor to the sense current Is. Theseresistance changes are processed as playback signals by the processingcircuitry 50 in FIG. 3.

[0041] The thicknesses and materials of the layers of the prior artsensor built and tested were 30 Å of Al₂O₃ for layer 212, 30 Å of NiMnOfor the layer 214, 25 Å of NiFeCr for the layer 216, 150 Å of Pt₅₀Mn₅₀for the layer 208, 13 Å of Co₉₀Fe₁₀ for the layer 232, 8 Å of Ru for thelayer 230, 20 Å of CO₉₀Fe₁₀ for the layer 234, 20 Å of Cu for the layer202, 9 Å of Co₉₀Fe₁₀ for the layer 218, 15 Å of Ni₈₄Fe₁₆ for the layer220, 6 Å of Cu for the layer 224 and 40 Å of Ta for the layer 226.

[0042] In a first test of Example 1 the example was tested at a couponlevel. The results were that the prior art spin valve sensor 200 had adesirable high magnetoresistive coefficient dr/R of 9.16 %. The netintrinsic uniaxial anisotropy field H_(Ki) was 30 Oe perpendicular tothe ABS. The magnetostriction M_(S) of the AP pinned layers was+1.5E-05. It is desirable that the magnetostriction M_(S) be positive sothat this, in combination with compressive stress in the head, willresult in a magnetostriction uniaxial anisotropy field which is orientedperpendicular to the ABS. The magnetostriction uniaxial anisotropy fieldH_(Kλ) of each AP pinned layer was about 300 Oe perpendicular to theABS. Accordingly, if the pinning layer 208 was removed from the spinvalve sensor 200 in FIG. 10, the AP pinned layer structure 204 would beself-pinned by a total uniaxial anisotropy field from each AP pinnedlayer of about 330 Oe. The resistance Rs of the sensor was 23 ohms/sq.and the magnetostriction λ of the free layer structure 206 was−7.64E-07. It is desirable that the magnetostriction of the free layerbe negative since this, in combination with compressive stress in thesensor, results in the free layer structure having a magnetostrictionuniaxial anisotropy field parallel to the ABS, as shown at 240 in FIG.10, which stabilizes the free layer.

[0043] In a second test of Example 1 the example was tested at the rowlevel for its amplitude output. The amplitude output of the prior artsensor, exemplified by Example 1, was 875 microvolts.

Example 2

[0044] In a first experiment involving Example 2 the spin valve sensor300 in FIG. 11 was tested at the coupon level and differed from the spinvalve sensor 200 in FIG. 10 in that the AP pinned layer structure 306had a first AP pinned layer (AP1) 308 was composed of Co₆₀Fe₄₀. Thesecond AP pinned layer 234 stayed the same as the second AP pinned layer234 in FIG. 10. The layer 304 was kept at 150 Å of Pt₅₀Mn₅₀ so as tofunction as an AFM pinning layer.

[0045] The magnetoresistive coefficient dr/R of the sensor 300 was 9.11%which is similar to the magnetoresistive coefficient dr/R of 9.16% forthe sensor 200 in FIG. 10. The intrinsic uniaxial anisotropy H_(Ki) forthe layers was still about 30 Oe. The magnetostriction λ of the first APpinned layer 308 was +3.0E-5 which is double the magnetostriction hadthe layer been Co₉₀Fe₁₀. The magnetostriction uniaxial anisotropy fieldH_(Kλ) of the AP pinned layer 308 was 500 Oe which is significantlyhigher than the 300 Oe for the AP pinned layer 232 in the prior artsensor 200 in FIG. 10. Accordingly, the sensor 300 in FIG. 11 can bestrongly self-pinned so as to obviate the need for the AFM pinning layerand the magnetoresistive coefficient dr/R will remain high. Themagnetostriction λ of the free layer structure 206 was −4.00E-07. Theresistance Rs of the sensor was 23.3 ohms/sq.

[0046] In a second test of Example 2 at the row level the layer 304 waschanged to 30 Å of Pt₅₀Mn₅₀, which is significantly below the thicknessrequired to function as a pinning layer, and the sensor was formed withan ABS. After these modifications the AP layer structure wasself-pinned. Testing after the modifications showed the sensor to havean amplitude of 1225 microvolts which is 40% higher than the amplitudeof the prior art sensor in Example 1. This is a significant improvementin the sensitivity of the sensor because of the self-pinning AP pinnedlayer structure 306 and the materials employed therein. Without thethick AFM pinning layer there is less sense current I_(S) shunting andthe read gap distance between the first and second shield layers 80 and82 has been significantly reduced to increase the linear read bitdensity of the read head.

[0047] The direction of the magnetic moment 238, either into or out ofthe sensor, is determined by the direction in which the magnetic momentis set by an external magnetic field without an elevated temperature.With the arrangement shown in FIG. 11 the magnetic field has beenapplied out of the sensor which causes the magnetic moment 238 to bedirected out of the sensor. If the external field is reversed in itsdirection the magnetic moment 238 would be directed into the sensor.When the AP pinned layers 308 and 234 are formed by sputter depositionthey are deposited in the presence of a field which is orientedperpendicular to the ABS. In this manner, the easy axes of the first andsecond AP pinned layers will likewise be oriented perpendicular to theABS.

Example 3

[0048] The spin valve sensor 400 in FIG. 12, which was tested at thecoupon level, was the same as the spin valve sensor 300 in FIG. 11except the AP pinned layer structure 402 had a first AP pinned layer(AP1) 404 which was composed of 13 Å of Co₉₀Fe₁₀ and a second AP pinnedlayer (AP2) 406 which was composed of 20 Å of Co₆₀Fe₄₀. The layer 304was kept at 150 Å of Pt₅₀Mn₅₀ so as to function as a pinning layer andthe ABS was not formed.

[0049] The magnetoresistive coefficient dr/R of the sensor 300 was 8.07%which is a considerable drop from the 9.11% for the spin valve sensor200 in FIG. 10. The intrinsic uniaxial anisotropy field H_(Ki) for eachAP pinned layers 308 and 234 remained at about 30 Oe, themagnetostriction λ of the first AP pinned layer 308 remained at +3.0E-5and the magnetostriction uniaxial anisotropy field H_(Kλ) of the APpinned layer 406 was about 500 Oe. The magnetostriction λ of the freelayer 206 was −7.29E-07. The resistance R_(S) of the sensor was 21.6ohms square.

[0050] In the invention the layer 304 in FIG. 12 is exemplified by 30 Åof Pt₅₀Mn₅₀ so that the layer 304 serves as a seed layer (SL4) and notan AFM pinning layer. Since the AP pinned layer 406 has a H_(Kλ) whichis significantly higher than the H_(Kλ) of the prior art AP pinned layer234 in FIG. 10, the AP pinned layer structure 402 in FIG. 12 will bestrongly self-pinned.

Example 4

[0051] The spin valve sensor 500 in FIG. 13, which was tested at thecoupon level, is the same as the spin valve sensor 400 in FIG. 12 exceptthe AP pinned layer structure 502 has a first AP pinned layer (AP1) 504which is composed of 13 Å of Co₆₀Fe₄₀. The layer 304 was kept at 150 Åof Pt₅₀Mn₅₀ so as to function as a pinning layer and the ABS was notformed.

[0052] The magnetoresistive coefficient dr/R of the sensor was 8.01%which is a considerable drop from the 9.11% for the sensor 300 in FIG.11. The intrinsic uniaxial anisotropy field H_(Ki) of the layersremained at about 30 Oe, the magnetostriction λ of each of the layerswas +3.0E-5 and the magnetostriction uniaxial anisotropy field H_(Kλ) ofthe AP pinned layers 504 and 406 were about 500 Oe. The magnetostrictionλ of the free layer structure 206 was −2.58E-07.

[0053] In the invention the layer 304 in FIG. 13 is exemplified by 30 Åof Pt₅₀Mn₅₀ so that the layer 304 serves as a seed layer (SL4) and notan AFM pinning layer. Since the AP pinned layers 504 and 406 have H_(Kλ)values of 500 Oe which are significantly higher than the H_(Kλ) valuesof the prior art AP pinned layers 232 and 234 in FIG. 10, the AP pinnedlayer structure 502 in FIG. 13 will be strongly self-pinned.

Example 5

[0054] The spin valve sensor 600 in FIG. 14, which was tested at thecoupon level, is the same as the spin valve sensor 500 in FIG. 13 exceptthe AP pinned layer structure 602 has a first AP pinned layer (AP1) 604which is composed of 13 Å of Co₉₀Fe₁₀ and a second AP pinned layer (AP2)606 is a lamination. The layer 304 was kept at 150 Å of Pt₅₀Mn₅₀ so asto function as a pinning layer and the ABS was not formed. The second APpinned layer 606 has a second AP pinned film (AP2B) 608 which is locatedbetween first and second AP pinned layer films (AP2A) and (AP2C) 610 and612. The second film 608 is composed of 5 Å of Co₆₀Fe₄₀, the first film608 is composed of 5 Å of Co₉₀Fe₁₀ and the third film 610 is composed of10 Å of Co₉₀Fe₁₀. The magnetoresistive coefficient dr/R was 8.91% whichis similar to the magnetoresistive coefficient of 9.16% for the spinvalve sensor 200 in FIG. 10. The intrinsic uniaxial anisotropy fieldH_(Ki) for each of the AP pinned layers 604 and 606 was about 30 Oe, themagnetostriction λ of the Co₆₀Fe₄₀ was +3.0E-5 and the magnetostrictionuniaxial anisotropy field H_(Kλ) of the AP pinned layer 606 was about400 Oe. The magnetostriction λ of the free layer structure 206 was−4.07E-07. The resistance R_(S) of the sensor was 23.4 ohms square.

[0055] In the invention the layer 304 in FIG. 14 is exemplified by 30 Åof Pt₅₀Mn₅₀ so that the layer 304 serves as a seed layer (SL4) and notan AFM pinning layer. The AP pinned layer 606 will have a H_(Kλ) ofabout 400 Oe, which is higher than the H_(Kλ) of the prior art AP pinnedlayer 234 in FIG. 10. The AP pinned layer structure 402 in FIG. 12 canbe strongly self-pinned.

Example 6

[0056] The spin valve sensor 700 in FIG. 15 is the same as the spinvalve sensor 600 in FIG. 14 except the AP pinned layer structure 702 hasa first AP pinned layer (AP1) 704 which is composed of 13 Å of Co₆₀Fe₄₀.This sensor was not built and tested, however, it combines theattributes of Examples 1 and 5 and is considered to be within the spiritof the invention.

[0057] The chart hereinbelow summarizes the results from the Examplesdescribed hereinabove. Co₆₀Fe₄₀ Experiments Position dR/R R_(s) ExampleInserted (%) H_(Ki) λ(AP) H_(Kλ) (Ω/sq) λ(FL) 1 Prior 9.16 30 Oe+1.5E−05 300 Oe 23.0 −7.64E−07 Art 2 AP1 9.11 30 Oe +3.OE−5 500 Oe 23.3−4.00E−07 3 AP2 8.07 30 Oe +3.OE−5 500 Oe 21.6 −7.29E−07 4 AP1/ 8.01 30Oe +3.OE−5 500 Oe 21.5 −2.58E−07 AP2 30 Oe +3.OE−5 500 Oe 5 AP2 * 8.9130 Oe +1.9E−5 400 Oe 23.4 −4.07E−07 6 AP1/ AP2 *

[0058] Discussion

[0059] It can be seen from the chart that Example 2 has a dr/R which iscomparable to Example 1 while having a significantly higher H_(Kλ) forself-pinning the AP pinned layer structure. While the self-pinning inExample 3 remains high the dr/R has significantly dropped as compared toExamples 1 and 2. A similar result was obtained with Example 4. However,Example 5 had a high self-pinning AP pinned layer structure and a dr/Rwhich is comparable to Example 1. As stated hereinabove, Example 6 is acombination of the desirable attributes of Examples 2 and 5.

[0060] While not preferred, it should be understood that the addition ofanother element in the cobalt iron (CoFe) content of the first andsecond AP pinned layers does not depart from the spirit of theinvention. It should be further understood that the invention can beemployed with top spin valves in addition to the bottom spin valvesdescribed hereinabove and can also be applied in dual spin valvesinstead of the single spin valve described hereinabove. It should befurther understood that the AP pinned layers may include additional APpinned layers separated by ruthenium layers instead of the two AP pinnedlayers separated by one ruthenium layer described hereinabove. Allembodiments can be employed in the structures shown in FIGS. 1-9.

[0061] The spin valve sensor described herein is a current in plane(CIP) spin valve sensor since the sense current I_(S) is conductedparallel to the major thin film planes of the sensor as shown in FIGS.11-15. The inventive concepts described herein also apply to a currentperpendicular to the planes (CPP) spin valve sensor where the sensecurrent I_(S) is conducted perpendicular to the major thin film planesof the sensor. Further, the inventive concepts are applicable tomagnetoresistive sensors other than spin valve sensors such as a tunneljunction sensor where a tunneling current is conducted through thesensor in a direction perpendicular to the major thin film planes of thesensor. Still further, the slider supporting the magnetoresistive sensormay have a head surface other than the aforementioned ABS such as a tapesurface for use in a tape drive.

[0062] The following commonly assigned U. S. Patents are incorporated intheir entirety by reference herein: (1) U.S. Pat. No. 5,465,185; (2)U.S. Pat. No. 5,583,725; (3) U.S. Pat. No. 5,768,069; (4) U.S. Pat. No.6,040,961; (5) U.S. Pat. No. 6,117,569; (6) U.S. Pat. No. 6,127,053; and(7) U.S. Pat. No. 6,219,211 B1.

[0063] Clearly, other embodiments and modifications of this inventionwill occur readily to those of ordinary skill in the art in view ofthese teachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

We claim:
 1. A magnetic head assembly comprising: a read head thatincludes a magnetoresistive sensor; the magnetoresistive sensorincluding: an antiparallel (AP) pinned layer structure; a ferromagneticfree layer having a magnetic moment that is free to rotate in responseto a field signal; and a spacer layer located between the free layer andthe AP pinned layer structure; the antiparallel (AP) pinned layerstructure including: ferromagnetic first and second antiparallel (AP)pinned layers; an antiparallel coupling (APC) layer located between andinterfacing the first and second AP pinned layers; the first and secondAP pinned layers self pinning one another without assistance of anantiferromagnetic (AFM) pinning layer; the second AP pinned layerinterfacing the spacer layer; each of the first and second AP pinnedlayers being composed of cobalt iron (CoFe); and the iron (Fe) contentin the cobalt iron (CoFe) of one of the first and second AP pinnedlayers being greater than the iron (Fe) content in the cobalt iron(CoFe) in the other of the first and second AP pinned layers.
 2. Amagnetic head assembly as claimed in claim 1 including: nonmagneticelectrically nonconductive first and second read gap layers; the spinvalve sensor being located between the first and second read gap layers;ferromagnetic first and second shield layers; and the first and secondread gap layers being located between the first and second shieldlayers.
 3. A magnetic head assembly as claimed in claim 2 furthercomprising: a write head including: ferromagnetic first and second polepiece layers that have a yoke portion located between a pole tip portionand a back gap portion; a nonmagnetic write gap layer located betweenthe pole tip portions of the first and second pole piece layers; aninsulation stack with at least one coil layer embedded therein locatedbetween the yoke portions of the first and second pole piece layers; andthe first and second pole piece layers being connected at their back gapportions.
 4. A magnetic head assembly as claimed in claim 3 wherein thefree layer is located between the AP pinned layer structure and thefirst pole piece layer.
 5. A magnetic head assembly as claimed in claim2 wherein the iron (Fe) content in the cobalt iron (CoFe) in the firstAP pinned layer is greater than the iron (Fe) content in the cobalt iron(CoFe) in the second AP pinned layer.
 6. A magnetic head assembly asclaimed in claim 5 wherein the first AP pinned layer comprises Co₆₀Fe₄₀and the second AP pinned layer comprises Co₉₀Fe₁₀.
 7. A magnetic headassembly as claimed in claim 2 wherein the iron (Fe) content in thecobalt iron (CoFe) in the second AP pinned layer is greater than theiron (Fe) content in the cobalt iron (CoFe) in the first AP pinnedlayer.
 8. A magnetic head assembly as claimed in claim 7 wherein thesecond AP pinned layer includes: a second film located between first andthird films with each film being composed of cobalt iron (CoFe); theiron (Fe) content in the cobalt iron (CoFe) in the second film beinggreater than the iron (Fe) content in the cobalt iron (CoFe) in each ofthe first and third films.
 9. A magnetic head assembly as claimed inclaim 8 wherein the second film comprises Co₆₀Fe₄₀ and each of the firstand third films comprises Co₉₀Fe₁₀.
 10. A magnetic head assembly asclaimed in claim 8 wherein the first AP pinned layer comprises Co₆₀Fe₄₀.11. A magnetic head assembly as claimed in claim 10 wherein the secondfilm comprises Co₆₀Fe₄₀ and each of the first and third films comprisesCo₉₀Fe₁₀.
 12. A magnetic disk drive including at least one magnetic headassembly that has a head surface and that includes a write head and aread head, comprising: the write head including: ferromagnetic first andsecond pole piece layers that have a yoke portion located between a poletip portion and a back gap portion; a nonmagnetic write gap layerlocated between the pole tip portions of the first and second pole piecelayers; an insulation stack with at least one coil layer embeddedtherein located between the yoke portions of the first and second polepiece layers; and the first and second pole piece layers being connectedat their back gap portions; the read head including a magnetoresistivesensor; the magnetoresistive sensor including: an antiparallel (AP)pinned layer structure; a ferromagnetic free layer having a magneticmoment that is free to rotate in response to a field signal; and aspacer layer located between the free layer and the AP pinned layerstructure; the antiparallel (AP) pinned layer structure including:ferromagnetic first and second antiparallel (AP) pinned layers; anantiparallel coupling (APC) layer located between and interfacing thefirst and second AP pinned layers; the first and second AP pinned layersself pinning one another without assistance of an antiferromagnetic(AFM) pinning layer; the second AP pinned layer interfacing the spacerlayer; the iron (Fe) content in the cobalt iron (CoFe) of one of thefirst and second AP pinned layers being greater than the iron (Fe)content in the cobalt iron (CoFe) in the other of the first and secondAP pinned layers; a housing; a magnetic medium supported in the housing;a support mounted in the housing for supporting the magnetic headassembly with said head surface facing the magnetic medium so that themagnetic head assembly is in a transducing relationship with themagnetic medium; a motor for moving the magnetic medium; and a processorconnected to the magnetic head assembly and to the motor for exchangingsignals with the magnetic head assembly and for controlling movement ofthe magnetic medium.
 13. A magnetic disk drive as claimed in claim 12wherein the free layer is located between the AP pinned layer structureand the first pole piece layer.
 14. A magnetic disk drive as claimed inclaim 12 wherein the iron (Fe) content in the cobalt iron (CoFe) in thefirst AP pinned layer is greater than the iron (Fe) content in thecobalt iron (CoFe) in the second AP pinned layer.
 15. A magnetic diskdrive as claimed in claim 14 wherein the first AP pinned layer comprisesCo₆₀Fe₄₀ and the second AP pinned layer comprises Co₉₀Fe₁₀.
 16. Amagnetic disk drive as claimed in claim 12 wherein the iron (Fe) contentin the cobalt iron (CoFe) in the second AP pinned layer is greater thanthe iron (Fe) content in the cobalt iron (CoFe) in the first AP pinnedlayer.
 17. A magnetic disk drive as claimed in claim 16 wherein thesecond AP pinned layer includes: a second film located between first andthird films with each film being composed of cobalt iron (CoFe); theiron (Fe) content in the cobalt iron (CoFe) in the second film beinggreater than the iron (Fe) content in the cobalt iron (CoFe) in each ofthe first and third films.
 18. A magnetic disk drive as claimed in claim17 wherein the second film comprises Co₆₀Fe₄₀ and each of the first andthird films comprises Co₉₀Fe₁₀.
 19. A magnetic disk drive as claimed inclaim 17 wherein the first AP pinned layer comprises Co₆₀Fe₄₀.
 20. Amagnetic disk drive as claimed in claim 19 wherein the second filmcomprises Co₆₀Fe₄₀ and each of the first and third films comprisesCo₉₀Fe₁₀.
 21. A method of making a magnetic head assembly comprising thesteps of: forming a read head that includes a magnetoresistive sensor; amaking of the magnetoresistive sensor including the steps of: forming anantiparallel (AP) pinned layer structure; forming a ferromagnetic freelayer that has a magnetic moment that is free to rotate in response to afield signal; and forming a spacer layer between the free layer and theAP pinned layer structure; the forming of the antiparallel (AP) pinnedlayer structure including the steps of: forming ferromagnetic first andsecond antiparallel (AP) pinned layers with the second AP pinned layerinterfacing the spacer layer; forming an antiparallel coupling (APC)layer between and interfacing the first and second AP pinned layers; thefirst and second AP pinned layers being further formed to self pin oneanother without assistance of an antiferromagnetic (AFM) pinning layer;forming each of the first and second AP pinned layers of cobalt iron(CoFe); and forming the cobalt iron (CoFe) of one of the first andsecond AP pinned layers with an iron (Fe) content that is greater thanthe iron (Fe) content in the cobalt iron (CoFe) in the other of thefirst and second AP pinned layers.
 22. A method of making a magnetichead assembly as claimed in claim 21 including the steps of: formingnonmagnetic electrically nonconductive first and second read gap layerswith the spin valve sensor located therebetween; and formingferromagnetic first and second shield layers with the first and secondread gap layers located therebetween.
 23. A method of a making magnetichead assembly as claimed in claim 22 further comprising the steps of:making a write head including the steps of: forming ferromagnetic firstand second pole piece layers in pole tip, yoke and back gap regionswherein the yoke region is located between the pole tip and back gapregions; forming a nonmagnetic electrically nonconductive write gaplayer between the first and second pole piece layers in the pole tipregion; forming an insulation stack with at least one coil layerembedded therein between the first and second pole piece layers in theyoke region; and connecting the first and pole piece layers at said backgap region.
 24. A method as claimed in claim 23 wherein the free layerstructure is formed between the AP pinned layer structure and the firstpole piece layer.
 25. A method as claimed in claim 22 wherein the cobaltiron (CoFe) of the first AP pinned layer is formed with an iron (Fe)content that is greater than the iron (Fe) content in the cobalt iron(CoFe) of the second AP pinned layer.
 26. A method as claimed in claim25 wherein the first AP pinned layer is formed to comprise Co₆₀Fe₄₀ andthe second AP pinned layer is formed to comprise Co₉₀Fe₁₀.
 27. A methodas claimed in claim 22 wherein the cobalt iron (CoFe) of the second APpinned layer is formed with an iron (Fe) content that is greater thanthe iron (Fe) content in the cobalt iron (CoFe) of the first AP pinnedlayer.
 28. A method as claimed in claim 27 wherein forming the second APpinned layer further includes the steps of: forming a second filmbetween first and third films with each film composed of cobalt iron(CoFe); forming the cobalt iron (CoFe) of the second film with the iron(Fe) content greater than the iron (Fe) content in the cobalt iron(CoFe) of each of the first and third films.
 29. A method as claimed inclaim 28 wherein the second film is formed to comprise Co₆₀Fe₄₀ and eachof the first and third films is formed to comprise Co₉₀Fe₁₀.
 30. Amethod as claimed in claim 28 wherein the first AP pinned layer isformed to comprise Co₆₀Fe₄₀.
 31. A method as claimed in claim 30 whereinthe second film is formed to comprise Co₆₀Fe₄₀ and each of the first andthird films is formed to comprise Co₉₀Fe₁₀.